Waves (unit 3)

Question 1

Wavelength = ?

Units?

Answer 1

Wave speed = wavelength * frequency

Wave speed (m/s)
Wavelength (m)
Frequency (Hz)

Question 2

Frequency = ?

Answer 2

F = 1/T

Frequency (Hz)

Question 3

Refractive index = ?

using the speed of light

Answer 3

Refractive index = speed of light in air / speed of light in medium

or

n = C in air / C in medium

Question 4

Refractive index = ?

using sin

Answer 4

Refractive index = sin(i) / sin(r)

Question 5

Two types of waves?

• Define
• Give examples of each (3)

Answer 5

LONGITUDINAL

• The vibrations of the wave are along the same direction of energy transfer
• Ultrasound, seismic waves and slinky when you push the end

TRANSVERSE

• The vibrations of the wave are at 90 degrees to the direction of energy transfer
• EM waves, ripples of water and slinky spring when waved up and down

Question 6

Define total internal reflection

Answer 6

When angle C (critical angel) is smaller than the angel of incidence. This means that all rays are reflected and none are refracted.

Question 7

Explain polarisation and give an example

Answer 7

• Only transverse waves can be polarised.
• Transverse waves are polarised when their vibrations are restricted to one plane only

e.g.

Sunglasses that reduce glare

Question 8

When does it happen?

1-Refraction

2-Diffraction

3-Reflection

Answer 8

1-Wave travels through a material but changes direction. The angel of refraction is less than the angel of incidence

2-Waves spread out when they meet a gap. The more narrow the gap the more the wave is diffracted

2-When waves rebound off material such as a plane mirror

Question 9

Critical angel?

Sin(C) = ?

Answer 9

1/n

Question 10

List the EM waves starting from the one with the lowest frequency

Answer 10

RADIO WAVES
MICRO WAVES
INFRARED 
VISIBLE
ULTRAVIOLET
X-RAY
GAMMA RAY